The advantages of fiber optic distributed measurement systems are substantial, including the ability to measure parameters of interest at large numbers of spatially distinct points over great distances. Exemplary measurands may include temperature, pressure, strain and disturbances of unknown natures.
Despite the benefits of distributed sensors, there are many instances where it may be desirable to improve the transduction from the measurand to the resultant optical signal and provide a much more specific and sensitive response. In addition to reducing the cross-sensitivity to other measurands, a more specific and sensitive response may provide information regarding certain characteristics of the measurand that otherwise may not be available. For instance, while a distributed vibration sensor may provide information to indicate the presence of a disturbance at a particular location, the measurement may not provide quantitative or directional information, thus potentially limiting a distributed system's usefulness in systems in which such parameters are of interest. Another limitation of distributed sensing systems can be the poor linearity of their response to a measurand (i.e., the transduction from the measurand to the generated optical signal) which also places constraints on the quality of the measurements that may be obtained.